The present invention relates to graft copolymers of a vinyl halide monomer, such as a vinyl chloride, or of a vinyl halide monomer and a comonomer copolymerizable therewith, on a polyolefin, i.e. an olefin trunk polymer, and to methods of preparing such graft copolymer products. The present graft copolymer products are aptly produced using a liquid phase bulk polymerization process. The present process substantially reduces the residual vinyl halide monomer, e.g. vinyl chloride monomer, in the graft copolymerized product while yielding a product of consistent, reduced grain size and improved color. In addition, scale build-up in the reaction vessel or vessels during a liquid phase bulk polymerization process is substantially reduced. The graft copolymer products have improved molding characteristics and are useful in the production of films, coatings and molded articles, where smooth, even surface areas and good contact clarity are desired.
The vinyl halide-polyolefin graft copolymeric products of the present invention comprise a graft copolymer of a vinyl halide (or of a vinyl halide and a comonomer copolymerizable therewith) and a polyolefin. Such copolymer products are hereinafter referred to as "vinyl halide-polyolefin graft copolymers". Such copolymers may be produced by polymerizing a mixture of vinyl halide monomer with one or more ethylenically unsaturated comonomers (or more conveniently, a vinyl halide monomer alone) in the presence of an olefin trunk polymer reactant.
Suitable ethylenically unsaturated comonomer materials which can be used include: ethylene, propylene, butene-1,4,4-dimethylbutene-1, decene-1, styrene and its nuclear alpha-alkyl or aryl substituted derivatives, e.g. o-, m- or o-methyl, ethyl or butyl styrene; and halogenated styrenes, such as alpha-chloro-styrene; mono-olefinically unsaturated esters including, vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate vinyl benzoate, vinyl-p-chlorobenzoates, alkyl methacrylates, e.g. methyl, ethyl, propyl and stearyl methacrylate, alkyl crotonates, e.g. octyl crotonate; alkyl acrylates, e.g. methyl, 2-ethyl hexyl, stearyl acrylates; hydroxyether and tertiary butylamino acrylates, e.g. 2-ethoxy ethyl acrylate, isopropenyl esters, e.g. isopropenyl acetate; isopropenyl halides, e.g. isopropenyl chloride; vinyl esters of halogenated acids, e.g. vinyl alpha-chloroacetate, and vinyl alpha-bromo-propionate; allyl and methallyl esters, e.g. allyl chloride, allyl cyanide; allyl chlorocarbonate, allyl nitrate, allyl formate and allyl acetate and the corresponding methallyl compounds; esters or alkenyl alcohols, e.g. beta-ethyl allyl alcohol; halo-alkyl acrylates e.g. methyl and ethyl alpha-chloroacrylates; allyl alpha-cyanoacrylates, e.g. methyl alpha-cyanoacrylate; itaconates, e.g. monomethyl itaconate, diethyl itaconate, alcohol (C-3to C-8) itaconates; maleates, e.g. monomethyl maleate, diethyl maleate, alcohol (C-3 to C-8) maleates; and fumarates, e.g. monomethyl fumarate, diethyl fumarate, alcohol (C-3 to C-8) fumarates, and diethyl glutaconate; mono-olefinically unsaturated organic nitriles including, for example, fumaronitrile, acrylonitrile, methacrylonitrile, 1,1-dicyanopropene-1, and oleonitrile; mono-olefinically unsaturated carboxylic acids including, for example, acrylic acid, methacrylic acid, cinnamic acid, maleic and itaconic acids, maleic anhydride and the like. Amides of these acids, such as acrylamide, are also useful. Vinyl alkyl ethers and vinyl ethers, e.g. vinyl methyl ether, vinyl ethyl ether, vinyl 2-chloroethyl ether, vinyl cetyl ether, and the like; and vinyl sulfides, e.g. vinyl beta-chloroethyl sulfide, vinyl betaethoxyethyl sulfide, and the like can also be included as can diolefinically unsaturated hydrocarbons containing two olefinic groups in conjugated relation and the halogen derivatives thereof, e.g. butadiene-1,e; 2-methyl-butadiene-1,3; 2,3-dichlorobutadiene-1,3; and 2-bromo-butadiene-1,3, and the like.
The polyolefin component may be a homopolymer, bipolymer, terpolymer, tetrapolymer or higher copolymer of olefinic monomers. The olefin polymers can also contain the residue of a polyene, e.g. a non-conjugated diene as a monomer unit. Preferably, the polyolefin component is an elastomer.
Olefin homopolymers may be obtained by the polymerization of a suitable monomer, such as ethene, propene, i.e. propylene, butene-1, isobutene, octene, or 5-methylhexene-1.
Suitable comonomers for use in preparing the olefin trunk copolymers are those utilized to prepare the olefin trunk homopolymers as listed above, e.g. propene or butene-1 with ethene and the like. Suitable termonomers are those utilized to prepare the olefin trunk homopolymers and copolymers as disclosed above, such as propene, ethene and the like, as well as a polyene. Especially suitable polyene-derived ter- and higher copolymers can be prepared from olefin monomer mixtures containing up to 15 percent, preferably up to about 6 percent by weight, of the polyene (preferably non-conjugated), e.g. dicyclopentadiene, cyclooctadiene and other dienes with linear or cyclic chains. The polyolefin used may also be a halogenated polyolefin, e.g. a chlorinated, brominated or fluorinates polyolefin.
The polyolefins used as trunk polymers are characterized by being soluble, partially soluble or dispersible at the polymerization temperature and pressure in the liquid halide monomer reactant (or mixture thereof with comonomer copolymerizable with the vinyl halide), and in having, typically, monomeric units of 2 to 8 carbon atoms. The weight average molecular weight of the olefin polymers, copolymers, terpolymers and tetrapolymers can vary from about 50,000 to about 1,000,000 or higher. Preferred as polyolefin rubbers for use in preparing vinyl halide graft polymers for use in the invention are ethene-propene polyolefin elastomers and ethene-propene-diene polyolefin elastomers.
More particularly, the hydrocarbon olefin polymers which are suitable employed as trunk polymer reactant in the preparation of the present graft polymers is an elastomer having a weight average molecular weight of about 50,000 to 1,000,000, preferably, of about 50,000 to 300,000, which is soluble, partially soluble or dispersible in the liquid phase polymerization reaction mixture. The trunk polyolefin reactant is suitable selected from the group consisting of:
(A) a homopolymer of an aliphatic hydrocarbon olefin monomer of 2 to 8 carbon atoms; PA0 (B) a copolymer of 2 or more of said olefin monomers; and PA0 (C) a polymer of at least one of said olefin monomers and no more than 15 percent, based on the weight of the polymer, of a non-conjugated aliphatic hydrocarbon polyene of 4 to 18 carbon atoms wherein all of the carbon-to-carbon double bonds do not form a conjugated system.
Typically, the aliphatic hydrocarbon olefin monomer of the trunk polyolefin is ethene (i.e. ethylene), propene, butene-1, isobutene, octene or 5-methylhexene-1. Typically, the hydrocarbon polyene employed as an optional component of the trunk polyolefin is a linear of cyclic polyene, such as 1,4-hexadiene dicyclopentadiene, ethylidene norbornene and the mono- and di-Diels Alder adducts of cyclopentadiene. The polyene which is present in the polyene-modified trunk polymer is preferably a diene, and the proportion of the polyene in the trunk polymer is preferably no more than about 6 percent. The trunk polymer employed in preparing the graft polymer component of the present compositions is preferably a copolymer of two or more of the above-defined aliphatic hydrocarbon olefins (typified by ethylene-propylene copolymer rubber) or a polymer of at least one of said hydrocarbon olefin monomers and the polyene. An especially good graft polymer is obtained by employing as trunk polyolefin a terpolymer, i.e. ternary copolymer, of two different olefin monomers and a diene, for example, an ethylene-propylene-ethylidene norbornene elastomer.
The vinyl halide-graft copolymers of the polyolefin elastomers are prepared by polymerizing the vinyl halide in the presence of about 0.05 to about 20 percent, preferably about 1 to about 10 percent, more preferably 4 to about 10 percent, based on the weight of vinyl halide monomer (or mixture thereof with a comonomer copolymerizable with vinyl halide) of the above-described polyolefin elastomer. Preparation of such vinyl halide-polyolefin graft copolymer according to emulsion and suspension polymerization techniques is described in G. Natta et al, U.S. Pat. No. 3,812,204, the disclosure of which is incorporated herein by reference. Preparation of such vinyl halidepolyolefin graft copolymer by vapor phase and solution polymerization techniques are described, respectively, in J. Dumoulin et al, U.S. Pat. No. 3,789,083 and F. M. Rugg et al, U.S. Pat. No. 2,947,719, the disclosures of which are incorporated herein by reference. Conveniently, the preparation of the vinyl halide-polyolefin graft copolymers useful as the polyvinyl halide component of the compositions of the invention is effected by a bulk liquid phase polymerization technique as described by A. Takahashi, U.S. Pat. No. 4,071,582; U.S. Pat. No. 4,163,033 and U.S. Pat. No. 4,169,870 and by L. E. Walker, U.S. Pat. Nos. 4,007,235; 4,067,928 and 4,195,137, the disclosure of which Takahashi and Walker patents is also incorporated herein by reference.
The vinyl halide-polyolefin graft copolymer, especially the graft copolymer product prepared by a liquid phase bulk polymerization reaction, has a substantially enhanced impact resistance at both ambient temperature and sub-ambient temperatures, compared to the conventional, i.e. ungrafted, vinyl halide polymers, even when the latter are blended with a conventional polyvinyl halide impact modifying polymer additive. The bulk polymerization prepared graft polymer product is even distinguished from the corresponding graft polymer prepared by a non-bulk polymerization technique, e.g. suspension polymerization, by an enhanced impact resistance at both low and ambient temperature and by breakage by the desirable ductile breakage mode rather than by an undesirable brittle breakage mode.
The present polymerization process may be carried out in one or more stages. The present process is particularly suited to be carried out using a two-stage liquid phase bulk polymerization process involving high speed agitation during a first stage in which about 3 to about 20 percent, preferably about 3 to about 15 percent, more preferably about 7 to about 12 percent, by weight of the monomer or monomers are converted to polymer and subsequently polymerization in a second stage involving low speed agitation for the remainder of the reaction.
The polymerization process is suitably carried out in a conventional stationary polymerization reaction zone employing therein a conventional, reaction mixture-inert agitator, i.e. an agitation body, such as a propeller, impeller, stirring paddle, screw, bar or blade. Such agitation body or bodies are movable, but are not freely movable in the polymerization reaction zone. This is so since the agitation body or bodies are movable only in direct response to an agitator motor means, e.g. a variable speed conventional agitator motor, the agitation body or bodies being connected thereto by a linking means, such as a mechanical drive shaft, a magnetic field or the like, which connection limits the movement of the agitation body within the stationary reaction zone. Such limitation of movement of the agitator is highly desirable, since it substantially avoids undesirable impact of the agitatory body against the reactor wall as in moving reactor processes. Two-stage polymerization processes and equipment are described in British Pat. No. 1,047,489 and U.S. Pat. No. 3,522,227, the teachings of which are hereby incorporated herein by reference.